The present invention relates generally to brake control values for operating a vehicles air brake system in response to brake pipe pressure and more specifically to an improved control valve.
Brake control valve systems for vehicles having air brakes generally include a brake control valve responsive to brake pipe pressure in a brake pipe to operate the brakes of a vehicle from a reservoir. For reduction of brake pipe pressure, the brakes are proportionally applied. For an increase in brake pipe pressure, the brakes may be released totally, known as direct release or gradually, known as graduated release. In AAR systems, the brake control valves include a service section and emergency section connected to a pipe bracket which are responsive respectfully to a service rate of reduction and an emergency rate of reduction to apply the brakes appropriately. Each section includes a separate diaphragm responsive to brake pipe pressure on one side and a reference pressure on the other. Not only do the brake control valve differentiate between a service and an emergency application, but they also must react in a specific amount of time to apply the brakes and to propagate the signal through the brake system to other cars.
The present control valves, as exemplified by the DB-60 from New York Air Brake or the ABDW from Wabco, include service (auxiliary) and emergency reservoirs with the service section applying the fluid from the service reservoir during a service brake application and the service and emergency sections providing service and emergency reservoir pressure during an emergency brake application. The service and emergency sections propagate service and emergency signals respectively. A release valve is associated with the service section and a retainer valve is also provided. Both of these control valves are a direct release system.
Historically and in non-AAR countries, the release system is considered a graduated release. This is where the brakes can be partially released no different than the brakes being gradually applied. Systems have been designed which have the ability to convert between a graduated and a direct release. Similar systems exist wherein combination with a simpler control valve, an emergency vent valve has been provided which senses an emergency braking condition on the brake pipe and propagates the signal by locally venting the brake pipe.
For certain brake applications, there is not a need for the sophisticated braking conditions found in the DB-60 and like control valves. Also, with the increased use of electropneumatic valve systems, there is a need for a simpler redundant pneumatic valve.
Thus, it is an object of the present invention to provide a simpler control valve.
Another object of the present invention is to provide a simpler control valve to be used with electro-pneumatic systems.
Still a further object of the present invention is to provide a control valve which combines graduated release with direct release over the release range.
Another object of the present invention is to provide a valve which is capable of plural sequential preliminary quick service.
A further object of the present invention is to provide a control which allows for minor adjustments of brake cylinder pressure without quick service.
An even further object of the present invention is to provide a control valve which has a graduated release during the initial period and terminating with a direct release or release ensuring.
Another object of the present invention is to provide a control valve which inhibits accelerated release transmission until the valve is in its direct release mode.
These and other objects are achieved by a brake control valve system having a pipe bracket with a single section control valve thereon working with a single reservoir, an emergency vent valve thereon and a manual release valve on the control valve. The single portion valve includes a first piston subject to brake pressure on one side, quick braking valve for connecting brake pipe pressure to a quick braking volume and a supply valve for connecting the reservoir to the brake cylinder and an exhaust valve for connecting brake cylinder to atmosphere. An operator mechanism controls the quick braking and supply valves in response to the position of the first piston so as to open the quick braking valve only when the supply valve is open. The supply valve may be opened without opening the quick braking valve. This is produced by the use of poppet valves and loss motion between the elements.
A choke is provided for continuously venting the quick braking volume to the atmosphere. A limiting valve is provided for disconnecting the quick braking valve from the quick braking volume when the brake cylinder pressure is 15 greater than the brake pipe pressure. This prevents the brake pipe from being vented through the first choke in a release after an emergency braking. An in-shot valve is provided between the reservoir and the brake cylinder.
In addition to the first piston which is subject to brake pressure on one side, a second coaxial piston is provided which is responsive to brake cylinder pressure on one side for controlling, with the first piston, the supply valve and exhaust valve to maintain a fixed ratio of brake cylinder pressure to brake pipe pressure reduction. Appropriate loss motion is provided between the first and second pistons as well as the second piston and the supply and quick braking valves. This allows supplying of the brake cylinder with the reservoir pressure by opening supply valve without opening the quick braking valve to maintain a given value in the brake cylinder.
An exhaust valve is provided for connecting the brake cylinder to atmosphere when opened by the first piston in response to an increase in brake pipe pressure which indicates a release. A control volume is provided preferably in the pipe bracket and the first piston is subject to control volume on a second side opposite the first side which has the brake pipe pressure. A charging valve connects the brake pipe to the reservoir and to the control volume when open. This valve permits charging of the reservoir and the control volume. The charging valve also controls the first piston to operate the exhaust valve in a graduated release mode for initial ranges of increased brake pipe pressure and the charging valves open for a full release of the brakes for a final range of increased brake pipe pressure in a direct release made. The opening of the charging valve interconnects both sides of the first piston to ensure that it goes into the fully released mode and also provides an increase in brake pipe pressure from the supply reservoir and the control volume to increase the propagation of the direct release down the brake pipe.
An emergency relay valve connects the reservoir to the supply valve when the brake cylinder pressure is below a first value compared to the control volume pressure.
An emergency accelerator release mechanism is also provided. It includes a dissipation valve which connects brake pipe and the brake cylinder when the brake cylinder pressure is a first value greater than the brake pipe pressure. An accelerator release valve connects the dissipation valve to the brake pipe and is opened when the brake pipe pressure is above a minimum value. Upon release or recharging after an emergency application, first the accelerator release valve is opened, providing brake pipe on one side of the dissipation valve. Since the brake cylinder has a greater pressure than the brake pipe, the dissipation valve is opened and brake cylinder is bled into the brake pipe and thereby increases the pressure in the brake pipe. This propagates the brake pipe release signal. It should be noted that the brake cylinder exhaust valve has not opened yet. As the brake pipe pressure builds up, the brake cylinder exhaust valve opens after the dissipation valve closes. This exhausts the remainder of brake cylinder pressure to atmosphere instead of the brake pipe.
With respect to the overall system, the control volume and the quick braking volume are preferably in the pipe bracket. The control valve includes the first and second pistons, supply valve, quick braking valve, brake cylinder exhaust valve, dissipation valve, emergency accelerated release valve, emergency relay valve and in-shot valve. The emergency vent valve on the pipe bracket is responsive to the emergency rate of decrease of pressure, to vent the brake pipe at the pipe bracket to atmosphere to initiate and propagate emergency braking. The emergency vent valve does not provide any direct control of the brake cylinder. This is performed by the control valve. A manual release valve is mounted to the control valve for venting both the cylinder and the reservoir when manually actuated. The release valve completely vents the brake cylinder in response to manual actuation and vents the reservoir only during manual actuation.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.